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Anatomy of the diaphragm
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Central: Phrenic nervesPeripheral: T5-T11 intercostal nerves and subcostal nerves
Ok, so let’s begin by looking at the general structure of the diaphragm. It curves superiorly into right and left domes.
The sternal part, attaches to the posterior aspect of the xiphoid process; the costal part attaches to the internal surfaces of the 7th to the 12th ribs and their costal cartilages; while the lumbar part attaches to the medial and lateral arcuate ligaments, the L1 to L3 vertebral bodies and the intervertebral discs in between.
Now, the diaphragm is the chief muscle for inspiration; meaning that when it contracts, it helps us breathe in. During contraction, the central portion of the diaphragm depresses, increasing the volume of the thoracic cavity, which, in turn, increases the volume in the lungs.
This makes the intrapulmonary pressure fall below the atmospheric pressure, creating a partial vacuum that allows fresh air to be sucked in!
On the other hand, expiration is largely passive, meaning the diaphragm relaxes and rises, which decreases the volume of the thoracic cavity, and subsequently increases the intrapulmonary pressure to be above the atmospheric pressure, forcing the air in the lungs to be expelled out.
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